1. Field of the Invention
The present invention relates to an electronic timepiece that automatically switches time associated with daylight saving time.
2. Description of Related Art
A conventional electronic timepiece can switch a displayed time to daylight saving time (also referred to as DST) while daylight saving time is in effect. For example, there has been an electronic timepiece equipped with a function to receive a radio wave including information of the standard time of a certain area (hereinafter referred to as “standard time radio wave”) to correct time. Such an electronic timepiece can automatically acquire the information about whether daylight saving time is in effect in each area on the basis of a signal included in a time code signal transmitted from the transmitting station in each country.
In a case of a conventional electronic timepiece which needs to reduce power consumption, such as a wristwatch in particular, the standard time radio wave is received only once a day. Accordingly, there may be a case where a change to daylight saving time/standard time is not reflected in the time after the change, depending on the timing of receiving the standard time radio wave. In such a case, a user who is unfamiliar with daylight saving time, especially a person who lives in Japan, may not recognize that the time has already been changed to daylight saving time/standard time, resulting in a trouble. Even if the user recognizes the change to daylight saving time/standard time, it may be difficult for the user to manually switch the settings of the timepiece. In view of these circumstances, Japanese Unexamined Patent Application Publication No. 2000-171576 discloses a technique to acquire from JJY the information of preliminary notice that he time will be switched to daylight saving time/standard time. In this technique, on a day on which the time is switched to daylight saving time/standard time, the standard time radio wave is received twice, i.e., before and after the switching. On the other hand, Japanese Unexamined Patent Application Publication No. 2004-191263 discloses a technique to make the reception time of the standard time radio wave different between the period of daylight saving time and the period of standard time, so that the standard time radio wave is received immediately after the switching in each period.
On the other hand, there has been an electronic timepiece that stores therein in advance a table providing information of times and dates of start and end of daylight saving time for each city, the local time of which can be displayed with the electronic timepiece. Japanese Unexamined Patent Applications Publication No. 54-74473 and No. 7-27881 disclose an electronic timepiece that acquires implementation period of daylight saving time from a table. This electronic timepiece is automatically set forward one hour during the period of daylight saving time.
A conventional way of receiving the standard time radio wave, however, changes the time of receiving the standard time radio wave irrespective of convenience and intention of a user. Further, since switching between daylight saving time and standard time is performed at a different time depending on the city, the time of receiving the standard time radio wave is changed every time the user moves to another city, which is inconvenient. Furthermore, since it takes a few minutes to complete reception of the standard time radio wave, the switching may coincide with reception of the standard time radio wave if the reception time of the standard time radio wave is arbitrarily set. This may provide a user with inaccurate information.